Reel type slot machine having stepper motor monitoring system

Abstract

A reel-type slot machine includes a microprocessor driven game control circuit for randomly determining a game result and three reel assemblies each including a symbol-bearing reel driven by a stepper motor for displaying the game results. The stepper motors each include a permanent magnet rotor and four stator windings which respond to quadrature phase motor drive signals generated by the game control circuit to incrementally rotate the reels. A reel motion monitoring circuit senses back EMF on each stator winding to generate an error signal which inhibits play in the event a motor fails to respond to an applied drive signal or a reel is moved by tampering.

We claim: 
     
       1. A monitored drive apparatus for use in conjunction with a stepper motor having a plurality of stator windings and a magnetic rotor, comprising: motor drive means responsive to an applied stepper pulses for applying phase signals to said stator windings whereby said motor is caused to incrementally rotate with each stepper pulse; and   monitoring means coupled to at least a portion of said stator windings and responsive to back EMF signals induced therein for providing an alarm signal in the event the movement of said rotor is not in accordance with said stepper pulses.   
     
     
       2. A monitored drive apparatus as defined in claim 1 wherein said motor stator comprises a permanent magnet. 
     
     
       3. A display system as defined in claim 1 wherein said stepper motor comprises four stator windings, and said phase signals comprise quadrature signals. 
     
     
       4. A display system as defined in claim 1 wherein said monitoring means comprise a plurality of diodes each connected at one end to a respective one of said stator windings, and at its other end to an integration circuit which provides an output signal in response to changes in back EMF signals derived from said stator windings by said diodes. 
     
     
       5. A display system as defined in claim 1 wherein said monitoring means further include threshold means for providing said alarm signal in the event said integration signal exceeds a predetermined level. 
     
     
       6. A slot machine comprising: a rotatably mounted reel containing a plurality of game symbols;   a stepper motor rotatably coupled to said reel;   said stepper motor including a magnetic rotor and multiple stator windings;   a game control circuit responsive to a play command for randomly picking a game result and generating stepper pulses for causing said motor to position said reel in accordance with said game result;   a motor drive circuit responsive to said stepper pulses for applying phase signals to said stator windings whereby said motor is caused to incrementally rotate with each stepper pulse; and   monitoring means coupled to at least a portion of said windings and responsive to back EMF signals induced therein for providing an alarm signal in the event the movement of said reel is not in accordance with said stepper pulses.   
     
     
       7. A slot machine as defined in claim 6 wherein said motor stator comprises a permanent magnet. 
     
     
       8. A slot machine as defined in claim 6 wherein said stepper motor comprises four stator windings, and said phase signals comprise quadrature signals. 
     
     
       9. A slot machine as defined in claim 6 wherein said monitoring means comprise a plurality of diodes each connected at one end to a respective one of said stator windings and at their other end to an integration circuit which provides an output signal in response to changes in the signals derived from said stator windings by said diodes. 
     
     
       10. A slot machine as defined in claim 9 wherein said monitoring means further include threshold means for providing said alarm signal in the event said integration signal exceeds a predetermined level. 
     
     
       11. A display device for displaying the outcome of a game in a slot machine comprising: a rotatably mounted reel containing a plurality of game symbols;   a stepper motor rotatably coupled to said reel;   said stepper motor including a magnetic rotor and multiple stator windings;   a motor drive circuit responsive to applied stepper pulses for applying phase signals to said stator windings whereby said motor is caused to incrementally rotate with each stepper pulse; and   monitoring means coupled to at least a portion of said windings and responsive to back EMF signals induced wherein for providing an alarm signal in the event the movement of said reel is not in accordance with said stepper pulses.   
     
     
       12. A display device as defined in claim 11 wherein said motor stator comprises a permanent magnet. 
     
     
       13. A display device as defined in claim 11 wherein said stepper motor comprises four stator windings, and said phase signals comprise quadrature signals. 
     
     
       14. A display device as defined in claim 11 wherein said monitoring means comprise a plurality of diodes each connected at one end to a respective one of said stator windings, and at their other end to an integration circuit which provides an output signal in response to changes in the signals derived from said stator windings by said diodes. 
     
     
       15. A display device as defined in claim 11 wherein said monitoring means further include threshold means for providing said alarm signal in the event said integration signal exceeds a predetermined level. 
     
     
       16. A display device for displaying the outcome of a game in a slot machine comprising: a rotatably mounted reel containing a plurality of game symbols;   a stepper motor rotatably coupled to said reels;   said stepper motor including a magnetic rotor and four stator windings;   motor drive means responsive to an applied stepper pulse for applying quadrature phase signals to said stator windings whereby said motor is caused to incrementally rotate with each stepper pulse; and   monitoring means comprising a plurality of diodes each connected between a respective one of said stator windings and an integrating circuit for providing an alarm signal in the event said rotor does not incrementally rotate in accordance with said stepper pulses.   
     
     
       17. A display device as defined in claim 16 wherein said monitoring means further include threshold means for providing said alarm signal in the event said integration signal exceeds a predetermined level.